Disc drives are digital data storage devices which store and retrieve large amounts of user data in a fast and efficient manner. The data are magnetically recorded on the surfaces of one or more rigid data storage discs affixed to a spindle motor for rotation at a constant high speed. The discs and spindle motor are commonly referred to as a disc stack.
The disc stack is accessed by an array of vertically aligned data transducing heads which are controllably positioned by an actuator assembly. Each head typically includes electromagnetic transducer read and write elements which are carried on an air bearing slider. The slider acts in a cooperative hydrodynamic relationship with a thin layer of air dragged along by the spinning discs to fly each head in a closely spaced relationship to the disc surface.
In order to maintain the proper flying relationship between the heads and the discs, the heads are attached to and supported by flexible suspension assemblies (flexures). An actuator motor (typically a voice coil motor, VCM) rotates the actuator assembly to cause the heads to move across the disc recording surfaces. The actuator assembly is also referred to as a head stack assembly (HSA). Both the disc stack and the HSA are mounted to and supported by a rigid base deck of the drive.
Disc drives of the present generation are typically manufactured using high volume automated assembly lines. In a typical automated line, each drive is assembled on a pallet that is conveyed to various assembly stations, with each station adding a different set of components to or performing a different operation upon the drive.
One such station is commonly referred to as a head-disc merge station in which an HSA is merged with a disc stack. The term “merge” in this context refers to the insertion and positioning of the heads into the disc stack (i.e., the positioning of the heads between and adjacent to the discs) in the final desired operational relationship.
In some merge operations the HSA and the disc stack are merged and then the merged HSA and disc stack are concurrently mounted to the base deck. Other merge operations mount the disc stack to the base deck, mount the HSA onto the base deck with the heads at a position outside the outermost diameter of the disc stack, and then rotate the HSA to merge the heads into the disc stack.
Typically, at the conclusion of a merge operation the heads are positioned near an innermost diameter of the disc stack and come to rest against texturized landing zones defined on the disc surfaces. The landing zones provide reduced stiction forces between the heads and discs and thus allow the heads to safely park during non-operation of the drive.
A latching arrangement secures the HSA when the heads are parked to prevent the heads from inadvertently moving out onto the data recording surfaces in response to application of a mechanical shock to the drive, since allowing the heads to come into contact with the data recording surfaces when the discs are not rotating can result in damage to the drive.
It is thus generally necessary to support the heads above the respective disc surfaces during the merge operation to place the heads in the final desired parked position. While prior art techniques have been proposed to apply power to the spindle motor to rotate the discs and to apply power to the actuator motor so that the heads are supported by air bearings established by disc rotation during the merge operation, it is generally more common to perform the merge operation while the discs are stationary (nonrotating) and to use appropriate tooling to support and advance the heads to the parked position.
The HSAs are typically sourced by an HSA manufacturer and are provided with removable shipping combs, which are comb-like structures that individually support the flexures to protect the heads from being jostled against one another and to prevent deformation of the flexures during shipping and handling.
During a typical merge operation, a merge comb (also merge tool, merge spreader) is inserted into the HSA by the merge station to provide the appropriate spacing between the heads. Once the heads are supported by the merge comb, the shipping comb is removed and the merge comb advances the heads to the final parked position.
Preferably, the merge comb supports the flexures and the heads as the heads are moved from the outermost diameter of the discs to the innermost diameter of the discs in such a manner so that no contact occurs between the disc stack and either the merge comb or HSA until the merge comb releases the heads in the final parked position. Once the heads are parked, the merge comb is retracted and the process is completed.
While the use of prior art merge combs during the merge process has been found to be effective, yield losses have nevertheless been observed partially due to misalignment of the HSA and/or the shipping comb with the merge comb. A primary failure mode has been linked to the merge comb not contacting and supporting the flexures in the appropriate location, leading to damage of the HSA and/or the discs due to mechanical interference between the discs and the HSA.
There is therefore a continued need for improvements in the art to address these and other limitations associated with the prior art, and it is to such improvements that the claimed invention is addressed.